Many optical fiber cables are pre-connectorized loose tube cables which comprise a plurality of optical fibers. Because the optical fibers are thin and fragile, the pre-connectorized loose tube cables have various members along the length of the fibers for protecting the fibers from becoming bent or stressed, such as a buffer tube, an inner tension member extending along the length of the cable, and/or outer sheaths. The protective members reduce any signal loss or fiber breakage by limiting the amount in which the optical fibers are bent or otherwise exposed to external forces, such as tensile forces.
When the optical fibers in an optical cable are to be spliced to other fibers or components, the fibers must be separated from many of the protective members in the cable and routed to their respective coupling locations. Typically, each optical fiber is separated from the outer sheaths and the tension member and is routed within a single buffer tube with a number of other fibers toward the coupling locations for the fibers. At a region close to the termination points for the fibers, a fiber break-out separates the fibers within the buffer tube from each other and routes the individual fibers within respective furcation tubes to their respective coupling locations. The specific coupling locations for the optical fibers can vary but are often locations in a fiber distribution shelf or a splice closure.
In routing the optical fibers in a cable to their respective coupling locations, however, the optical fibers can become damaged within the furcation tube or within the buffer tube. Often, the individual optical fibers and their respective furcation tubes are bundled together within a spiral tube and routed as a group to the distribution shelf or closure. The optical fibers and furcation tubes can become intertwined with each other within the spiral tube and, at times, become so twisted that some of the optical fibers become bent or kinked, thereby introducing a signal loss or causing the fiber to break. The entanglement of the fibers within the spiral tube is therefore a problem when routing the fibers in a pre-connectorized loose tube cable to their points of termination. Additionally, when the fibers do become entangled, it is time consuming to untangle them so that each fiber may be directed to its proper location.
As is typical in the industry, the total length of each fiber is greater than the required distance so as to provide a slack length of fiber for the technician. When routing the fibers within a pre-connectorized loose tube cable to a distribution shelf, or similar type of unit, the slack length of buffer tube length is looped into coils and attached to the distribution shelf. The buffer tubes may also be gathered together within a spiral tube and routed from the end of the sheath toward the connectors in the distribution shelf.
Another significant cause of fiber bending is due to the routing of the buffer tubes, including the looping of the buffer tubes to reduce the amount of slack. The buffer tubes are typically comprised of polybutylene terephthalate (PBT), which is easily bent or kinked if the buffer tubes should become bent, such as in routing the fibers within the spiral tube or in looping the buffer tubes to reduce slack. When the buffer tube becomes kinked, the fibers within the buffer tube are bent at a sharp angle causing signal loss and, if the bend is less than the minimum allowable bend radius for the fibers, causing fiber breakage.
Because the fibers can easily break within the buffer tubes, the technician must take great care when handling the buffer tubes so as to prevent any kinking of the tubes. The time spent by the technician in handling the buffer tubes thus becomes relatively long whereby, as a consequence, the entire time for coupling a pre-connectorized loose tube cable to a distribution shelf is significantly increased.
One approach to reducing the chance that the buffer tubes will become kinked is to reduce the overall length of the buffer tubes. In this manner, the buffer tubes may not need to be looped in order to reduce the slack. While a shorter buffer tube may reduce the chance that the fibers become bent due to a kink in the buffer tube, a shorter buffer tube increases the distance that the fiber is contained within only the furcation tube. Because the optical fibers are more vulnerable to external forces when within the furcation tube only, the fibers are preferably contained within the buffer tube rather than the furcation tube. Thus, even though the buffer tubes may cause fiber breakage due to a kink in the buffer tube, the fibers are preferably left within the buffer tube in order to protect the fibers.
A need therefore exists for a device or method for protecting optical fibers as the fibers are being routed, such as from a pre-connectorized loose tube cable to the coupling points for the fibers. The device or method for protecting the fibers must be able to bend so that the fibers can be routed to the coupling points, yet cannot bend past the minimum bend radius for the optical fibers. A need also exists for a device or method for permitting a technician to couple a pre-connectorized loose tube cable in a shorter period of time than has heretofore been possible.